Iron Swarm has four boss designs, and this page is their reference card. Each entry below is organised the same way — where the boss shows up, how much health it carries, the health breakpoints that flip it into a new phase, the attacks it uses, and the single visual tell that warns you what is coming. The idea is that you can scan straight to the boss in front of you and read its facts at a glance. This is deliberately a reference: it lists what each boss does, not the moment-to-moment tactics for beating it. For the how — where to stand, when to dodge, when to commit damage — the Iron Swarm Strategy Guide has a dedicated per-boss tactics section, and the Game Modes page explains which modes put these bosses in front of you. New to the fight? Start with How to Play, or jump into a battle.
How bosses fit into a run
Bosses arrive on a fixed rhythm: combat runs in four-round cycles, and the fourth round of each cycle is a boss instead of a wave (the Daily Challenge caps its run with a boss on round five). Every boss is multi-phase, and every one of them gets tougher the further you go — across cycles a boss gains roughly ten percent more health, twelve percent more speed, and ten percent faster fire, so the same design that felt comfortable early becomes a genuine test later. The phase breakpoints listed below are the constant; the raw numbers scale underneath them.
Standard boss
The Standard boss is the first multi-phase fight most players meet, and it is the template the others build on — a mobile tank whose attack set widens in two clean steps as its health falls.
- Role: the all-rounder that introduces the multi-phase format.
- Phase breakpoints: keyed to its health at 70% and 30%.
- Above 70%: single straight shots only.
- 70% to 30%: adds a three-bullet spread, a full 360-degree ring burst on a timer, and a ramming charge.
- Below 30%: the spread widens to five bullets and the ring burst becomes denser and faster.
- Signature tell: the charge — it accelerates and rams for collision damage, and it does not weaken with the difficulty scaling, so it stays the attack you must always be primed to sidestep.
Glacier Warden
The Glacier Warden opens fast and mobile, then re-roots itself for a very different closing phase, so in effect it asks you to learn two bosses in one fight.
- Role: a mobile, aggressive boss early that changes character late.
- Signature attack: a frost cone — a wide 45-degree fan of bullets.
- Signature tell: a pulsing cyan arc that fills at its barrel tip over about a second before the cone fires. When the arc completes, the fan is coming.
- Final phase: it stops moving and begins laying mines on a timer, each one flagged first with a red marker on the floor.
- What flips: the danger moves from the boss to the ground — once it is rooted it stops chasing, but the arena fills with mines you have to keep clear of.
Bastion
The Bastion is the odd one out: it is bolted to the spot and fights entirely through firepower and the turrets it summons, so the whole duel is about the ground around it rather than chasing it down.
- Role: a stationary fortress that never moves; the whole fight is about its volleys and the space around it.
- Primary attack: triple shots in a tight spread that punish standing still.
- Adds: it spawns turrets, so the arena grows extra threats you have to clear.
- Final phase: an overcharge shot — a single heavy round.
- Signature tell: before the overcharge, the three barrel tips ramp in colour from green to amber to white over roughly six-tenths of a second. That colour ramp is your warning to already be out of the firing line.
Iron Commander
The Iron Commander is the Campaign's capstone and the only boss with a hard-set health total, built around a punishing counter-shot that turns your own aggression against you.
- Role: the Campaign's final boss, met at Chapter 6, round 24.
- Health: a fixed 762 HP (it does not use the standard per-cycle health scaling).
- Base attack: a three-round burst cannon throughout the fight.
- Phase breakpoints: at 60% and 30% health.
- From 60%: it begins counter-shooting — when one of your rounds passes close to it, it fires a mirrored shot back along that line after a short delay.
- Below 30%: it glows red-hot, gains about twenty percent more speed, adds an overcharge spread shot with the same green-to-amber-to-white barrel tell, starts dropping mines, and its counter-shot delay shortens so the punish lands faster.
- Signature mechanic: the counter-shot — the reason careless point-blank fire is dangerous against it.
Cross-boss quick reference
A few traits repeat across the roster, and spotting the pattern makes an unfamiliar boss quicker to read:
- The colour-ramp tell (green → amber → white) means an overcharge shot is charging. It appears on both the Bastion and the Iron Commander — the same visual language, so learning it once covers two bosses.
- Mine-dropping in the late fight is shared by the Glacier Warden and the Iron Commander. In both, the closing phase turns the floor into a hazard, so late-fight footwork matters as much as dodging shots.
- Going stationary late is the Glacier Warden's and the Bastion's story — a rooted boss gives you a clean damage window but usually pairs it with a new area threat (mines or turrets).
- Phase intensity climbs as health falls for every boss: expect more bullets, wider spreads, and faster patterns the lower the health bar goes.
Where to go next
That is the data. To turn it into wins, the Strategy Guide walks through the actual tactics for each of these bosses — dodging the tells above and picking your damage windows — and the power-ups, hazards, and terrain reference covers the mines, cover, and pickups that shape every boss arena. When you are ready to test it, play Iron Swarm free in your browser.